Methods and apparatus to control heat dissipation in hard-disk drives

ABSTRACT

Methods and apparatus to control heat dissipation in hard-disk drives (HDDs) are disclosed. A disclosed example apparatus comprises a semiconductor die, a ground bump positioned on the die, and a hard-disk drive writer head positioned on the die relative to the ground bump based on a thermal impedance.

RELATED APPLICATIONS

This patent claims the benefit of U.S. Provisional Application Ser. No.60/988,541, entitled “Footprint of Preamp Writer Heads,” filed on Nov.16, 2007, and which is hereby incorporated by reference in its entirety.

FIELD OF THE DISCLOSURE

This disclosure relates generally to hard-disk drives, and, moreparticularly, to methods and apparatus to control heat dissipation inhard-disk drives.

BACKGROUND

Hard-disk drives (HDDs) use one or more disks and/or platters thatrotate about a spindle with respect to one or more heads, such as readand/or writer heads. The read or writer heads read information fromand/or impart information to the disk platters, but do not, in desiredoperation, physically contact the platters. Traditionally, a HDD head isimplemented by an integrated circuit (IC) that is subsequently mounted(e.g., soldered) to a printed circuit substrate (e.g., a printed circuitboard (PCB) and/or a printed circuit cable assembly (PCCA). The printedcircuit substrate is affixed to a stiffener and/or armature arm thatpositions the HDD head relative to a disk platter.

FIG. 1 is a top cross-sectional view of an example armature assembly 100for a HDD. In the illustrated example of FIG. 1, things that are insection are shown as dotted blocks. The armature assembly 100 includes,among other things, a printed circuit substrate 105, and an IC 110 thatimplements four HDD writer heads 115-118. As shown, the HDD writer heads115-118 are positioned at the edge of the IC 110 to, for example,shorten a trace length from solder bumps of the writer heads 115-118(one of which is designated at reference numeral 120) to othercomponents, circuits and/or devices of the printed circuit substrate105.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top cross-sectional view of an example prior art armatureassembly for a hard-disk drive (HDD).

FIG. 2 is a schematic diagram of an example HDD constructed inaccordance with the teachings of the invention.

FIG. 3 is a side-view showing additional detail of an example manner ofimplementing the example armature assembly of FIG. 2.

FIG. 4 is a top cross-sectional view of the example armature assembly ofFIG. 3.

FIG. 5 is a graph illustrating example thermal impedance improvementsthat may be achieved by positioning a HDD writer head based on thermalconductivity principles described herein.

FIG. 6 is a flowchart of an example process that may be carried out toposition a HDD writer head on an integrated circuit (IC).

FIG. 7 is a schematic illustration of an example processor platform thatmay be used and/or programmed to execute the example process of FIG. 6to place a HDD writer head on an IC as described herein.

DETAILED DESCRIPTION

As shown in FIG. 2, a hard-disk drive (HDD) system 200 of a computer mayinclude one or more platters 205, 206 that rotate about a spindle 210.One or more armature assemblies (one of which is designated at referencenumeral 215), which pivot about an axis 220, are provided above and/orbelow the platters 205, 206. The example armature assembly 215 of FIG. 2includes one or more HDD read and/or writer heads (one example writerhead is designated at reference numeral 225) for reading informationfrom and/or writing information to the platters 205, 206. In the writecontext, the example HDD writer head 225 is coupled to a drive headcontroller 230, which processes a write signal 235 and provides one ormore signals to the writer head 225 and/or, more generally, the armatureassembly 215 to cause data associated with the write signal 235 to bewritten to one or more of the platters 205, 206.

FIG. 3 illustrates a side-view showing additional details of an examplemanner of implementing the example armature arm assembly 215 of FIG. 2.The example armature assembly 215 of FIG. 3 includes an armature arm340, a stiffener 330, a printed circuit substrate 315 (e.g., a printedcircuit board (PCB) and/or a printed circuit cable assembly (PCCA))having one or more copper and/or ground planes 325, and an integratedcircuit (IC) 305 that implements the example HDD writer head 225. Theexample HDD writer head 225 of FIG. 3 is positioned within the IC 305 tocontrol how well heat is conducted from the HDD writer head 225 to otherportions of the armature assembly 215. That is, how well the heat isbeing conducted from the HDD writer head 225 to one or more of thecopper and/or ground plane 325 of the printed circuit substrate 315, thestiffener 330 and/or the armature arm 340. In some examples, the HDDwriter head 225 is positioned within the IC 305 to minimize a thermalimpedance from the HDD writer head 225 to the armature arm 340. However,the HDD writer head 225 may be positioned within the IC 305 to decreasethe thermal impedance subject to other design constraints, such as clockspeed, signal skew, noise, etc.

As described above, to implement the example HDD writer head 225, theexample armature assembly 215 of FIG. 3 includes the example IC 305. Theexample IC 305 may be, for example, a semiconductor die onto whichcircuits (e.g., the example HDD writer head 225), components, devices,traces, etc. are depositing using any number and/or type(s) of siliconmanufacturing processes. The example IC 305 is constructed as aso-called “flip-chip”, which is also referred to in the industry as acontrolled collapse chip connection (C4) type of mounting. However, anytype of package and/or mounting may be used to construct the IC 305. Forexample, the IC 305 may include one or more semiconductor dice, one ormore bonding wires and a semiconductor package. Compared to some othertypes of chip packages, the example IC 305 of FIG. 3 has a plurality ofsolder bumps (one of which is designated at reference numeral 310)instead of wire bonds. The example solder bumps 310 of FIG. 3 may be,for example, constructed by depositing solder onto chip pads of the IC305, which are located on the top side of the IC 305, during a finalwafer processing step. The example IC 305 is mounted to the printedcircuit substrate 315 by “flipping” the chip such that the top of the IC305 is facing down towards a mounting area of the example printedcircuit substrate 315. The solder bumps 310 are then re-melted (e.g.,using ultrasound) to adhere the IC 305 to the printed circuit substrate315. Once the IC 305 is affixed to the printed circuit substrate 315,circuits (e.g., the example HDD writer head 225), nodes, devices and/ortraces of the IC 305 become electrically coupled to circuits, nodes,traces (two of which are designated at reference numerals 320 and 321),and/or copper and/or ground planes (one of which is designated atreference numeral 325) of the example printed circuit substrate 315. Insome examples, the mounted IC 305 is then under filled using anelectrically-insulating adhesive (not shown).

Typically a set of solder bumps 311 of the IC 305 are dedicated toand/or used to provide coupling of ground signals and/or ground tracesof the example IC 305 to a ground plane (e.g., the example plane 325) ofthe example printed circuit substrate 315. As used herein, such solderbumps 311 will be referred to as “ground bumps,” to delineate theirpurpose from other solder bumps (e.g., the solder bump 310) used toelectrically couple other types of signals. As described more fullybelow in connection with FIG. 4, the example HDD writer head 225 of FIG.3 is positioned within and/or located on the IC 305 to control how wellheat can be conducted from the HDD writer head 225 to the ground plane325 and, thus, to other portions of the example armature assembly 215.Subject to any other design and/or layout constraints (e.g., clockspeed, signal skew, noise, etc.), the example writer head 225 of FIG. 3is located relative to (e.g., as close as possible to) one or moreground bumps 311 to increase (e.g., maximize) the amount of heat(generated by operation of the writer head 225) that is conducted by thenearby ground bumps 311 to the ground plane 325. That is, the examplewriter head 225 is purposefully located on the IC 305 to lower thethermal impedance of the silicon junctions that comprise the writer head225. Such a lowering of the thermal impedance allows, for example, thatthe writer head 225 may be operated at higher clock frequencies and/orfacilitates better thermal stability of the printed circuit substrate315 and/or, more generally, the entire armature assembly 215. Incontrast, traditional HDD ICs have their writer heads placed within theIC without regard to thermal constraints. For example, placing them atthe edges of an IC for ease of routing within the IC and/or a printedcircuit substrate to which the IC is mounted, as describe above inconnection with FIG. 1.

To increase the rigidity of the example printed circuit substrate 315,the example armature assembly 215 of FIG. 3 includes a stiffener 330. Inmodern HDDs, sufficient rigidity of the printed circuit substrate 315 isimportant, while the HDD is operating, to controlling and/or maintaininga separation between the example writer head 225 and a platter (e.g.,the example platter 205 of FIG. 2). The example stiffener 330 of FIG. 3includes one or more mounts (e.g., holes and associated screws thatallow the example printed circuit substrate 315 to be mechanicallyattached to the stiffener 330. In addition to increasing the rigidity ofthe printed circuit substrate 315, the example stiffener 330 also servesas part of a thermal conductivity path 335 between the writer head 225and an armature arm 340.

The example armature arm 340 of FIG. 3 is controlled by, for example,the drive head controller 230 of FIG. 2, to position the writer head 225relative to a HDD platter, such as the example platter 205. The examplearmature arm 340 also serves as a thermal sink for heat generated by thewriter head 225 and conducted to the armature arm 340 via the thermalconduction path 335.

FIG. 4 illustrates a top cross-sectional view of the example armatureassembly 215 of FIG. 3 taken along a section line 350. In theillustration of FIG. 4, items that are section are shown as dottedblocks. Portions of the example armature assembly 215 of FIG. 4 areidentical to those discussed above in connection with FIG. 3 and, thus,the descriptions of those portions are not repeated here. Instead,identical elements are illustrated with identical reference numerals inFIGS. 2 and 3, and the interested reader is referred back to thedescriptions presented above in connection with FIG. 3 for a completedescription of those like-numbered elements.

As illustrated in FIG. 4, the example writer head 225 is positionedwithin the IC 305 so that the writer head 225 is close to one or moreground bumps 405. By locating the writer head 225 near to the groundbumps 405, heat can be readily conducted from the writer head 225 to theground bumps 405, and from the ground bumps 405 via one or more traces(one of which is designated at reference numeral 410) of the printedcircuit substrate 315 to a ground plane 415 of the printed circuitsubstrate 315. In the illustrated example of FIG. 4, the example IC 305implements three additional writer heads 420-422 that are likewiselocated nearby to additional ground bumps 425-426. An example thermaldesign constraint and/or rule lays out, designs, locates, positionsand/or orients the writer heads 420-422 on the IC 305 such a distance(one of which is designated at reference numeral 423) from anysignificant heat generating solder bump of a writer heads 225, 420-422(e.g., a solder bump associated with a preamp) to a ground bump 405,425, 426 is no greater than a dimension 424 of the writer heads 225,420-422.

While an example manner of implementing the example armature apparatus215 of FIG. 2 is illustrated in FIGS. 3 and 4, an armature apparatus maybe implemented using any number and/or type(s) of alternative and/oradditional logic, devices, components, circuits, modules, interfaces,etc. Further, the logic, devices, components, circuits, modules,elements, interfaces, etc. illustrated in FIGS. 3 and/or 4 may becombined, divided, re-arranged, omitted, eliminated and/or implementedin any other way. For example the example stiffener 330 and the examplearmature arm 340 could be combined into a single module, and/or adifferent number of writer heads (e.g., eight) could be implemented byan IC and/or an armature assembly. Moreover, an armature assembly mayinclude additional logic, devices, components, circuits, interfacesand/or modules instead of, or in addition to those illustrated in FIGS.3 and/or 4.

FIG. 5 is a graph illustrating example thermal impedance improvementsthat may be achieved by positioning HDD writer heads as describedherein. Thermal impedance values are shown for combinations of thenumber of writer heads per the example IC 305 (four and eight), andwhether the writer heads 225, 420-422 are placed near the edge of the IC305 (as illustrated in FIG. 1) or within an interior portion of the IC305 near to ground bumps (e.g., the example ground bumps 405, 425, 426as described above). As illustrated in FIG. 5, a five to ten percentdecrease in thermal impedance can be achieved by positioning HDD writerheads 225, 420-422 based on thermal conductivity principles.

FIG. 6 is a flowchart representative of example process that may becarried out to locate and/or place HDD writer heads on an IC. Theexample process of FIG. 6 may be carried out by a processor, acontroller and/or any other suitable processing device. For example, theexample process of FIG. 6 may be embodied in coded instructions storedon a tangible medium such as a flash memory, a read-only memory (ROM)and/or random-access memory (RAM) associated with a processor (e.g., theexample processor P105 discussed below in connection with FIG. 7).Alternatively, some or all of the example process of FIG. 6 may beimplemented using any combination(s) of circuit(s), application specificintegrated circuit(s) (ASIC(s)), programmable logic device(s) (PLD(s)),field programmable logic device(s) (FPLD(s)), discrete logic, hardware,firmware, etc. Also, some or all of the example process of FIG. 6 may beimplemented manually or as any combination of any of the foregoingtechniques, for example, any combination of firmware, software, discretelogic and/or hardware. Moreover, the example process of FIG. 6 may beincorporated in design rules enforced by an IC design and/or layout tooland/or software. Further, although the example operations of FIG. 6 aredescribed with reference to the flowchart of FIG. 6, many other methodsof implementing the operations of FIG. 6 may be employed. For example,the order of execution of the blocks may be changed, and/or one or moreof the blocks described may be changed, eliminated, sub-divided, orcombined. Additionally, any or all of the example process of FIG. 6 maybe carried out sequentially and/or carried out in parallel by, forexample, separate processing threads, processors, devices, discretelogic, circuits, etc.

The example process of FIG. 6 begins by positioning grounds bumps 405 ona IC 305 of an IC 305 (block 605). Writer heads 225, 420-422 are thenpositioned on the IC 305 relative to the ground bumps 405 to improve athermal characteristic of the IC 305 (e.g., reduce a thermal impedance)(block 610). The remainder of components, circuits, devices and/ortraces of the IC 305 are then placed and/or laid out on the IC 305(block 615). Control then exits from the example process of FIG. 6.

Additionally or alternatively, the example process of FIG. 6 may beapplied iteratively wherein one or more layout constraints are verifiedupon completion of block 615. If one or more of the constraints are notmet, the process could be repeated after one or more design rules arerelaxed (e.g., a maximum distance between a writer head 225, 420-422 andground bumps 405 is increased). Moreover, a portion of the IC 305 may belaid out prior to the ground bumps 405 and/or writer heads 225, 420-422being placed.

FIG. 7 is a schematic diagram of an example processor platform P100 thatmay be used and/or programmed to layout a HDD IC in accordance with thewriter head placement methods and apparatus described herein. Theexample process platform P100 may, additionally or alternatively, beused and/or programmed to implement an IC design and/or layout tool thatincludes the writer head placement methods and apparatus describedherein. The example processor platform P100 can be implemented by one ormore general purpose processors, processor cores, microcontrollers, etc.

The processor platform P100 of the example of FIG. 7 includes at leastone general purpose programmable processor P105. The processor P105executes coded instructions P110 and/or P112 present in main memory ofthe processor P105 (e.g., within a RAM P115 and/or a ROM P120). Theprocessor P105 may be any type of processing unit, such as a processorcore, a processor and/or a microcontroller. The processor P105 mayexecute, among other things, the example process of FIG. 6 to implementthe example methods and apparatus described herein.

The processor P105 is in communication with the main memory (including aROM P120 and/or the RAM P115) via a bus P125. The RAM P115 may beimplemented by dynamic random access memory (DRAM), synchronous dynamicrandom access memory (SDRAM), and/or any other type of RAM device, andROM may be implemented by flash memory and/or any other desired type ofmemory device. Access to the memory P115 and the memory P120 may becontrolled by a memory controller (not shown).

The processor platform P100 also includes an interface circuit P130. Theinterface circuit P130 may be implemented by any type of interfacestandard, such as an external memory interface, serial port, generalpurpose input/output, etc. One or more input devices P135 and one ormore output devices P140 are connected to the interface circuit P130.

Although certain example methods, apparatus and articles of manufacturehave been described herein, the scope of coverage of this patent is notlimited thereto. On the contrary, this patent covers all methods,apparatus and articles of manufacture fairly falling within the scope ofthe appended claims either literally or under the doctrine ofequivalents.

1. An apparatus comprising: a semiconductor die; a ground bumppositioned on the die; and a hard-disk drive (HDD) writer headpositioned on the die relative to the ground bump based on a thermalimpedance.
 2. An apparatus as defined in claim 1, further comprising asecond ground bump positioned on the die, wherein the HDD writer head ispositioned on the die relative to both ground bumps based on the thermalimpedance.
 3. An apparatus as defined in claim 1, wherein the thermalimpedance is representative of a thermal conduction path from the HDDwriter head to a copper plane of a printed circuit board via the groundbump.
 4. An apparatus as defined in claim 1, wherein the HDD writer headis positioned on the die so that a solder bump associated with the HDDwriter head is no more than a length of the HDD writer head from theground bump to reduce the thermal impedance of the solder bump.
 5. Ahard-disk drive (HDD) armature apparatus comprising: a printed circuitsubstrate; and an integrated circuit (IC) comprising a HDD writer head,the HDD writer head positioned on the IC based on a thermal impedance ofthe HDD writer head.
 6. A HDD armature apparatus as defined in claim 5,further comprising: a stiffener to stiffen the printed circuitsubstrate; and an armature arm to position the HDD writer head relativeto a platter of a HDD, wherein the printed circuit substrate is attachedto the armature arm via the stiffener.
 7. A HDD armature apparatus asdefined in claim 6, wherein the thermal impedance is representative of athermal conduction path from the HDD writer head to the armature arm isvia the stiffener, a copper plane of the printed circuit substrate, anda ground bump of the IC.
 8. A HDD armature apparatus as defined in claim5, wherein the thermal impedance is representative of a thermalconduction path from the HDD writer head to a copper plane of theprinted circuit substrate via a ground bump of the IC.
 9. A HDD armatureapparatus as defined in claim 5, wherein the printed circuit substratecomprises at least one of a printed circuit board (PCB) or a printedcircuit cable assembly (PCCA).
 10. A method to design an integratedcircuit (IC) for a hard-disk drive (HDD), the method comprising:positioning a ground pin on the IC; and positioning a HDD writer head onthe IC relative to the ground pin based on a thermal conductance.
 11. Amethod as defined in claim 10, further comprising positioning the HDDwriter head on the IC relative to the ground pin based on the thermalconductance by positioning the HDD writer head so that a signal pinassociated with the HDD writer head is no more than a length of the HDDwriter head from the ground pin.
 12. A method as defined in claim 10,further comprising positioning a second ground pin on the IC, whereinthe HDD writer head is positioned relative to both ground pins based onthe thermal conductance.
 13. A method as defined in claim 10, whereinthe thermal conductance is representative of a thermal conduction pathfrom the HDD writer head to a copper plane of a printed circuitsubstrate via the ground pin.
 14. A method as defined in claim 10,wherein the ground pin is a ground bump of a flip-chip IC package. 15.An article of manufacture storing machine readable instructions which,when executed, cause a machine to: position a ground pin of anintegrated circuit (IC); and positioning a hard-disk drive (HDD) writerhead on the IC relative to the ground pin based on a thermalconductance.
 16. An article of manufacture as defined in claim 15,wherein the machine readable instructions, when executed, cause themachine to position the HDD writer head on the IC relative to the groundpin based on the thermal conductance by positioning the HDD writer headsuch that a signal pin associated with the HDD writer head is no morethan a length of the HDD writer head from the ground pin.
 17. An articleof manufacture as defined in claim 15, wherein the machine readableinstructions, when executed, cause the machine to: position a secondground pin on the IC; and position the HDD writer head relative to bothground pins based on the thermal conductance.
 18. An article ofmanufacture as defined in claim 15, wherein the thermal conductance isrepresentative of a thermal conduction path from the HDD writer head toa copper plane of a printed circuit substrate via the ground pin.